가시나 has several meanings depending on the context. There are 3 common usages. 1) noun. it means "little girl". it is a dialect of 계집애"little girl" Not much disrespectful but very informal word used for addressing between intimate female friends or mother to daughter. 2) verb. it means "t​horn grows". it is contracted form of 가시가 나. 가시(thorn) + 가(subject particle) + 나(grow)" 잎에 가시 나 The thorns grow on the leaf 3) verb. it means "Does she/he go". 가(go) + 시(honorific particle) + 나(interrogative ending suffix) 선생님은 언제 집에 가시나? When the teacher goes home?